Don't drop PHP7.0 compatibility for dev yet.
Created by: dawnbreak
There is no need yet to drop PHP7.0 compatibility for running tests in TravisCI. The next PHPUnit release in Feb 2018 will drop PHP7.0, but current version with PHP7.0 will be supported until 2019.
Composer gets a bit messy. We need to run composer update for our libraries in PHP5.6 as long as we support that version. When we update dev libraries we must run composer update in PHP7.0 so we can run all tests in TravisCI. semver and version constraints does not work reliable in any case, because there are libraries that deprecate PHP versions in minor updates and rely on composer platform requirements to handle the rest.